The invention concerns an electrical construction assembly, or an assembled electrical component, having a liquid crystal display on a circuit board with a sheet-metal screen for receiving, or retaining, the other elements and holding them together.
Such an electrical component is described in Belgium Patent Document 881 912. A combination comprising a circuit board, a liquid crystal display as well as contacts and spacers is effectively held together by a sheet-metal screen. In this regard, the sheet-metal screen overlaps the combination on three edges thereof, with a fourth edge serving as a terminal contact connection. Even with this mechanically very stable arrangement, there is, in retrospect, a recognizable defect which is expensive to eliminate and usually leads to, in this type of construction, a loss of the component.
A circuit board with a screwed on light conductor is disclosed in German Patent 32 47 531 A1. The light conductor supports on its upper surface a plurality of liquid crystal indicators to which ribs of the light conductor assign particular positions.
Electrical components of this type are often encountered on electrical apparatus, or appliances. For example, they are often behind apparatus front walls which frame an information surface of the liquid crystal's viewing side. Often, such front walls are additionally provided with keys, or switches, which allow, for example, a user to influence information read from the liquid crystal. Such keys, and possibly additional component elements, such as resistors, condensers, diodes, integrated circuits and so forth, as well as also light conductors with light sources, are often combined with a liquid crystal display on a common circuit board.
Known assembled electrical components are provided with a sheet-metal screen to reduce influences of thermal or electrical radiation. For electrical components, or construction assemblies, which are assembled at a place or time different from an end product, or for appliances whose front walls, including electrical components, are intentionally removable--for example for reasons of protecting against theft of car radios--sheet-metal screens of the components are also used as, and sometimes even predominantly, mounting frames for the components themselves or for holding and stiffening the components.
In order to hold a liquid crystal display on a circuit board, customized receivers for these types of displays are often used. Such a receiver includes a number of contact elements which elastically contact the liquid crystal display and, with correspondingly provided contact surfaces, link with, for example, a circuit board. Contact elements can also be formed as conductive rubber strips with alternating adjacent electrical insulators and conductor segments. A necessary pressure between the contact elements and the contact surfaces of the liquid crystal display to achieve a problem-free contact is created either by an appropriate shaping of the contact elements, for example forming a fork spring of the contact elements themselves, or by means of an addition holder or framing part mounted on the receiver. (DE-C1-37 26 225, DE-A1-41 05 505, EP-A2-0 493 071, DE-U-87 05 715, DE-U-88 01 014, DE-U-88 05 722). With such an arrangement for releasably holding a liquid crystal display on a circuit board, additional parts are always necessary which serve to hold the contact elements or the liquid crystal display in proper positions or to ensure good contacts upon providing background illumination of the liquid crystal display.
It is therefore an object of this invention to provide an assembled electrical component with a circuit board, a liquid crystal display, a light conductor, and a sheet-metal screen which, with regard to its mechanical structure, can be effectively fabricated without the necessity of additional parts and with small expenditures, and which can be maintained in this assembled configuration for, for example, operational inspection or for interim storing as well as for transportation to final mounting, and which, according to requirements, can be disassembled with an equally small expense.